Posterior chamber lens implant

ABSTRACT

A posterior chamber lens implant is disclosed for use after extracapsular surgery. In extracapsular surgery the interior of the lens of the human eye is evacuated through a surgical opening formed in the front membrane of the lens while leaving the rear membrane of the lens or posterior capsule intact. The lens implant comprises an optic having a front surface and a rear surface and the implant is secured within the posterior chamber of the eye. In one form of the invention, a ridge spaces the rear surface of the optic forwardly from the posterior capsule while in a second form of the invention, the rear surface of the optic is concavely formed to space the rear surface of the optic forwardly of the posterior capsule. The implant of the present invention thus facilitates laser posterior capsulotomy in the event of clouding of the posterior capsule following the extracapsular surgery.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to a posterior chamber lens implant foruse after extracapsular surgery.

II. Description of the Prior Art

In extracapsular surgery, a surgical opening is formed through the frontmembrane or anterior capsule of the lens of the human eye and thecateracts and fluid within the interior of the lens is surgicallyremoved. During such surgery, however, it is important to leave theposterior capsule of the lens intact so that it forms a barrier betweenthe vitreous humor and the aqueous humor. Removal of the posteriorcapsule is known to result in a high incidence of retinal detachment aswell as cystoid macular edema.

Following the removal of the cataracts, it is necessary to replace thehuman lens with an artificial lens implant in order to restore sight tothe eye. Although these lens implants may be nested in the anteriorchamber, i.e., behind the cornea, or in the pupil, it has been foundthat posterior chamber lens implants are medically superior to anteriorchamber and pupil lens implants for a plurality of reasons.

The previously known posterior chamber lens implants comprise an optichaving a convex front surface and generally planar rear surface. Thelens implant is nested within the posterior chamber and so that the rearsurface of the optic flatly abuts against the posterior capsule. Theoptic is typically secured in place in the posterior chamber by loops orhaptics extending outwardly from the optic and sandwiched between theposterior capsule and anterior leads.

In a high incidence of cases, after a period of time followingimplantation of the lens the posterior capsule becomes clouded andobscures the vision of the eye. In order to restore the vision to theeye after this has occurred, it is necessary to perform a posteriorcapsulotomy to remove the portion of the posterior capsule that isaligned with the optic.

In one previously known method to perform a posterior capsulotomy knownas discission, a needle is inserted into the eye and used to punch ahole through the posterior capsule and behind the optic. In many cases,however, the posterior capsule becomes tough following the extracapsularsurgery so that it is necessary to enter the eye with scissors in orderto cut a hole in the posterior capsule. Both discission and membranecutting, however, involve a significant risk of introducing bacteria orother contaminants into the eye which may ultimately result in loss ofthe eye.

In surgical procedure laser posterior capsulotomy, a laser is focused onthe posterior capsule through the pupil. Upon activation of the laser,the laser burns an opening through the posterior capsule behind theoptic thus restoring vision to the eye. The use of the laser in contrastwith the previously known discission and membrane cutting is highlyadvantageous in that laser surgery is noninvasive and thus eliminatesthe possibility of introducing bacteria or other contaminants into theeye.

At present, however, laser posterior capsulotomy can be performed onlyon an anterior chamber or pupil lens implant. In a posterior chamberlens implant, the rear surface of the implant flatly abuts against theposterior capsule so that destruction of the posterior capsule by thelaser may also result in destruction of the lens implant.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a posterior chamber lens implant whichenables a subsequent laser posterior capsulotomy to be performed, ifnecessary.

In brief, the lens implant of the present invention comprises an optichaving a front surface, a rear surface and means for securing the opticwithin the posterior chamber. Preferably, the securing means comprisesone or more haptics which are nested in between the posterior capsuleand the anterior leads of the cataract capsule.

Unlike the previously known posterior chamber lens implant, however, thepresent invention comprises means for spacing the rear surface of theoptic forwardly of the posterior capsule thus forming a space betweenthe rear surface of the optic and the posterior capsule. In thepreferred form of the invention, an annular ridge is formed around theouter periphery of the optic on its rear side so that the ridge extendsrearwardly from the optic. Consequently, following implantation of thelens into the posterior chamber, the ridge abuts against the posteriorcapsule and spaces the rear suface of the optic forwardly from theposterior capsule.

In a second preferred embodiment of the invention, the rear surface ofthe lens implant is concavely formed so that, with the lens positionedwithin the posterior chamber, only the outer periphery of the rear sideof the optic abuts against the posterior capsule. The remainder of therear surface of the optic is spaced forwardly of the posterior capsule.

In practice, only a relatively small spacing, for example, onemillimeter, is necessary between the rear surface of the lens implantand the posterior capsule in order to enable a laser posteriorcapsulotomy to be safely performed.

BRIEF DESCRIPTION OF THE DRAWING

A better understanding of the present invention will be had uponreference to the following detailed description, when read inconjunction with the accompanying drawing, wherein like referencecharacters refer to like parts throughout the several views, and inwhich:

FIG. 1 is a fragmentary sectional view illustrating a first preferredembodiment of the lens implant of the present invention within theposterior chamber;

FIG. 2 is a fragmentary sectional view taken substantially along line2--2 in FIG. 1;

FIG. 3 is a view taken substantially along line 3--3 in FIG. 1 and withparts removed for clarity;

FIG. 4 is a sectional view taken substantially along line 4--4 in FIG.3;

FIG. 5 is a view similar to FIG. 4 but showing a modification thereof;and

FIG. 6 is a view similar to FIGS. 4 and 5, but showing a secondpreferred embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

With reference first to FIGS. 1 and 2, a human eye 10 is thereshownfollowing extracapsular surgery. During extracapsular surgery, acircular opening 12 is formed in the anterior capsule 13 of the cataractcapsule 14, or lens, and the cataracts are removed from the interior ofthe capsule 14. In doing so, the posterior capsule 16 of the lens 14 isleft intact as well as an annular portion around the outer periphery ofthe anterior capsule 13 thus forming an annular anterior lead 18.

Referring now to FIGS. 1-3, a first preferred embodiment of theposterior chamber lens implant 20 of the present invention is thereshownand comprises a central optic 22 having a front convex surface 24(FIG. 1) and a generally planar rear surface 26. The optic 22, which istypically constructed of plastic, is designed to reproduce orapproximate the optical qualities of the lens of the human eye..Iadd.The optic is constructed of a material so that, with said opticimplanted within the posterior chamber, said optic maintains a rigidshape following implantation. .Iaddend.

As is best shown in FIGS. 3 and 4, an annular ridge 28 is formed aroundthe outer periphery on the rear surface 26 of optic 22 so that the ridge28 protrudes rearwardly from the optic 22. This ridge 28 is preferablycontinuous and integrally constructed with the optic 22. The ridge 28illustrated in FIG. 4 is generally semicircular in cross sectional shapealthough other shapes, such as a square cross sectional shape as shownfor the ridge 28' in FIG. 5, may alternatively be used.

With reference again to FIGS. 1 and 2, the lens implant 20 is positionedwithin the posterior chamber 30 of the eye 10 so that the ridge 28flatly abuts against the posterior capsule 16. In doing so, the ridge 28spaces the rear surface 26 of the optic 22 forwardly from the posteriorcapsule 16. This spacing, which is exaggerated in FIG. 1 for clarity, ispreferably less than a few millimeters.

Any conventional means may be used to secure the lens implant 22 withinthe posterior chamber 30. However, as shown in the drawing, one or morehaptics 32 are secured to and extend radially outwardly from the optic22. A portion 34 of each haptic is positioned between the posteriorcapsule 16 and the anterior lead 18. Following extracapsular surgery,the anterior lead 18 folds against the posterior capsule 16 thussandwiching the haptic portions 34 therebetween and securing the lensimplant 20 in place. The use of haptics 32 positioned in between theposterior capsule 16 and anterior lead 18 is well known in the art.

With reference now particularly to FIG. 6, a still further preferredembodiment of the lens implant 20' is thereshown and comprises an optic22' which is convex-o-concave in shape. As such, the optic 22' includesa front convex surface 24' and a rear concave surface 26'. Consequently,with the lens implant 20' positioned within the posterior chamber 30,only the outer periphery 36 of the optic 22' abuts against the posteriorcapsule 16 and spaces the central portion of the optic rear surface 26'forwardly from the posterior capsule 16.

It will be understood, of course, that still other constructions for thelens implant 20 may be used to space the rear surface 26 of the optic 22forwardly from the posterior capsule 16.

By spacing the rear surface 26 of the optic 22 forwardly from theposterior capsule 16, the present invention enables the safe use of alaser to perform a posterior capsulotomy in the event that the posteriorcapsule subsequently becomes clouded or obscured. As previouslydescribed, unlike discission and membrane cutting, laser posteriorcapsulotomy completely eliminates the possibility of bacterial infectionor the introduction of other contaminants into the eye.

Having described my invention, however, many modifications thereto willbecome apparent to those skilled in the art to which it pertains withoutdeviation from the spirit of the invention as defined by the scope ofthe appended claims.

I claim:
 1. A posterior chamber lens implant for a human eye for useafter extracapsular surgery in which a posterior capsule is leftsubstantially intact, said lens implant comprising:a substantiallycircular rigid optic having a front surface, a rear surface and asubstantially circular and continuous outer rear edge, said frontsurface being a continuous convex surface and said rear surface being acontinuous concavely curved surface extending between said outer rearedge, means for securing said optic to the eye within the posteriorchamber so that said outer rear edge abuts against the posterior capsuleand so that the rear concavely curved surface of said optic is spacedfrom the posterior capsule by a distance sufficient to safely allow asubsequent laser posterior capsulotomy. .Iadd.2. A posterior chamberlens implant for a human eye for use after extracapsular surgery inwhich a posterior capsule is left substantially intact, said lensimplant comprising: a substantially circular optic having a frontsurface, a rear surface and a substantially circular and continuousouter rear edge, said front surface being a continuous convex surfaceand said rear surface being a continuous concavely curved surfaceextending between said outer rear edge, means for securing said optic tothe eye within the posterior chamber so that said outer rear edge abutsagainst the posterior capsule and so that the rear concavely curvedsurface of said optic is spaced from the posterior capsule by a distancesufficient to safely allow a subsequent laser posterior capsulotomy,wherein said optic is constructed of a material so that, with said opticimplanted within the posterior chamber, said optic maintains a rigidshape following implantation. .Iaddend.